Substrate transfer apparatus for component mounting machine

ABSTRACT

A mounting-waiting process for making a substrate to be transferred into a mounting process wait before the mounting process; and a substrate discharge-waiting process for making the substrate transferred from the mounting process wait before the following process are provided. When transfer of an unmounted substrate into the mounting process and transfer of a mounted substrate from the mounting process to the substrate discharge-waiting process are performed simultaneously, it is detected, by a substrate-arrival detecting sensor for detecting the mounted substrate transferred to the substrate discharge-waiting process and a substrate-continuity detecting sensor for detecting the unmounted substrate continuously transferred following to the mounted substrate, that a plurality of substrates have been transferred into the discharge-waiting process continuously.

TECHNICAL FIELD

The present invention relates to a substrate transfer apparatus used in a component mounting machine such as an electronic component mounting machine, for example, for transferring a substrate from a mounting-waiting process to a mounting process.

BACKGROUND ART

As the above-mentioned type apparatus, a substrate transfer apparatus for an electronic component mounting machine shown in FIG. 5, for example, has been conventionally provided. FIG. 5 is a perspective view of an electronic component mounting machine 1 including a conventional substrate transfer apparatus; FIGS. 6A-6D are sequential views showing a substrate transfer process in the conventional substrate transfer apparatus; and FIGS. 7A-7D are sequential views showing a process of simultaneous transfer of substrates in the conventional substrate transfer apparatus. Among the above-listed figures, FIGS. 6A, 6C, 6D, 7A, 7C, and 7D are views of the substrate transfer apparatus seen from above the apparatus, while FIGS. 6B and 7B are views of the substrate transfer apparatus shown in FIGS. 6A and 7A, respectively, seen from the side of the apparatus.

In FIGS. 5, 6A-6D and 7A-7D, the reference numeral 2 denotes a mounted substrate; 3 an unmounted substrate; 4 a, 4 b and 4 c entrance substrate detecting sensors; 5 a, 5 b and 5 c substrate-arrival detecting sensors; and 10 a, 10 b and 10 c transfer belts. This substrate transfer apparatus has a mounting-waiting process 7, a mounting process 8 and a substrate discharge-waiting process 9. Arrows in FIGS. 5-7D represent a substrate transfer direction. According to such a conventional substrate transfer apparatus, by rotating the transfer belts 10 a, 10 b, and 10 c shown in FIG. 6B, the unmounted substrate 3 can be transferred from the mounting-waiting process 7 to the mounting process 8, and the mounted substrate 2 can be transferred from the mounting process 8 to the substrate discharge-waiting process 9 sequentially.

The above transfer process is described more specifically. In the processes shown in FIGS. 6A and 6B, the transfer belt 10 b is first rotated. After the entrance substrate detecting sensor 4 c detected the mounted substrate 2, the transfer belt 10 c is rotated to transfer the mounted substrate 2 into the substrate discharge-waiting process 9. The fact that the mounted substrate 2 has completely entered the substrate discharge-waiting process 9 can be determined by detecting that the entrance substrate detecting sensor 4 c of the substrate discharge-waiting process 9 was placed on a substrate-detected state after the rotation of the transfer belt and thereafter the state of the sensor 4 c turned into an undetected state.

By keeping the transfer belts 10 b and 10 c rotating and further rotating the transfer belt 10 a, the unmounted substrate 3 is transferred from the mounting-waiting process 7 to the mounting process 8. FIG. 6C shows a state immediately after the rotation of the transfer belt 10 a started.

After the state shown in FIG. 6C, upon detection of the mounted substrate 2 by the substrate-arrival detecting sensor 5 c of the substrate discharge-waiting process 9, the rotation of the transfer belt 10 c is stopped, thereby finishing the transfer of the mounted substrate 2 from the mounting process 8 to the substrate discharge-waiting process 9. Moreover, when the substrate-arrival detecting sensor 5 b of the mounting process 8 detected the unmounted substrate 3, the rotation of the transfer belt 10 b is stopped, thereby finishing the transfer of the unmounted substrate 3 from the mounting-waiting process 7 to the mounting process 8. FIG. 6D shows this state.

However, in the above-described transfer process, waiting time is generated from determination that the mounted substrate 2 has completely entered the substrate discharge-waiting process 9 to the start of the transfer of the unmounted substrate 3. In order to reduce the time required for the transfer operation, there is a method in which that waiting time is eliminated and the transfer of the mounted substrate 2 and that of the unmounted substrate 3 simultaneously start. For example, a method for simultaneously transferring a plurality of substrates is effective.

The aforementioned simultaneous transfer method is described more specifically, referring to a substrate transfer apparatus for transferring two substrates simultaneously as an example. In the process shown in FIGS. 7A and 7B, the transfer belts 10 a, 10 b, and 10 c are activated to rotate simultaneously. Thus, it is possible to simultaneously start the transfer of the mounted substrate 2 and the transfer of the unmounted substrate 3. FIG. 7C shows a state immediately after the transfer start of the mounted substrate 2 and unmounted substrate 3. Then, when the substrate-arrival detecting sensor 5 c in the substrate discharge-waiting process 9 has detected the mounted substrate 2, the rotation of the transfer belt 10 c is stopped. Moreover, when the substrate-arrival detecting sensor 5 b in the mounting process 8 has detected the unmounted substrate 3, the rotation of the transfer belts 10 a and 10 b is halted. As a result, the transfer of the mounted substrate 2 and unmounted substrate 3 is finished. This state is shown in FIG. 7D.

However, when the simultaneous transfer method is performed by using the conventional substrate transfer apparatus described above, a trouble may occur during the transfer of the preceding substrate, for example, the mounted substrate 2 may be got stuck during the transfer. In this case, there is a problem that the following substrate, such as the unmounted substrate 3, catches up with the preceding substrate having the trouble and, if the following substrate eliminates the trouble of the preceding substrate by the impact when the following substrate catches the preceding substrate, a plurality of substrates are transferred to the downstream process continuously.

FIGS. 8A-8D are diagrams showing a process of occurrence of the problem during the simultaneous transfer of a plurality of substrates in the conventional substrate transfer apparatus. In FIGS. 8A-8D, the reference numeral 2 denotes a mounted substrate; 3 an unmounted substrate; 4 a, 4 b and 4 c entrance substrate detecting sensors; 5 a, 5 b and 5 c substrate-arrival detecting sensors; and 10 a, 10 b and 10 c transfer belts. As is the case with FIGS. 5-7D, the reference numeral 7 denotes the mounting-waiting process; 8 the mounting process; and 9 the substrate discharge-waiting process. The arrow in FIGS. 8A-8D represents the substrate transfer direction.

The aforementioned problem is described more specifically, referring to simultaneous transfer of two substrates as an example. In the process shown in FIGS. 8A and 8B, the transfer of the mounted substrate 2 and the transfer of the unmounted substrate 3 are started simultaneously by starting to rotate the transfer belts 10 a, 10 b, and 10 c simultaneously. FIG. 8C shows a state in which the preceding mounted substrate 2 became stuck after the start of the rotation of the transfer belts 10 a, 10 b, and 10 c and the following unmounted substrate 3 caught up with the mounted substrate 2. If the mounted substrate 2 got out of the stuck state by the impact when the unmounted substrate 3 caught up with the mounted substrate 2, for example, the mounted substrate 2 and the unmounted substrate 3 are continuously transferred into the substrate discharge-waiting process 9 although the unmounted substrate 3 is to be stopped at the position of the substrate-arrival detecting sensor 5 b in the mounting process 8. This is because the transfer belts 10 b and 10 c are being rotated. FIG. 8D shows this state.

In a case where the substrate transfer apparatus comes into such a state, when a substrate-request signal was output from equipment connected in the downstream process of the electronic component mounting machine 1 and thus the rotation of the transfer belt 10 c was started so as to discharge the mounted substrate 2 c, the unmounted substrate 3 was also discharged to the equipment connected in the downstream process. As a result, there is a problem that a defective substrate is generated in which components to be mounted have not been mounted during the process in the electronic component mounting machine 1.

The present invention was made considering the aforementioned two problems. It is an object of the present invention to provide a substrate transfer apparatus for a component mounting machine, that includes detection means for detecting continuous transfer of a plurality of substrates, thereby reducing transfer time, preventing occurrence of a defective substrate in advance, and improving the quality of produced substrates.

DISCLOSURE OF INVENTION

In order to achieve the above object, a first aspect of the present invention is a substrate transfer apparatus for a component mounting machine, for transferring a substrate into a mounting process which mounts components onto the substrate and transferring the substrate from the mounting process. The apparatus of the present invention includes: a mounting-waiting process for making the substrate to be transferred into the mounting process wait before the mounting process; and a substrate discharge-waiting process for making the substrate after being transferred from the mounting process wait before a following process, wherein detecting means is provided for detecting, when transfer of an unmounted substrate from the mounting-waiting process to the mounting process and transfer of a mounted substrate for which mounting has been done in the mounting process from the mounting process to the substrate discharge-waiting process are simultaneously performed, that a plurality of substrates have been transferred into the substrate discharge-waiting process continuously. Thus, when a plurality of substrates is simultaneously performed, detecting means determines whether or not a plurality of substrates was continuously carried in from the previous process. Therefore, the first aspect of the present invention has an effect that the transfer of the unmounted substrate to a downstream equipment, that may occur when a plurality of substrates were continuously transferred into the following process, and occurrence of a defective substrate caused by that transfer can be prevented in advance.

A second aspect of the present invention is to form the detecting means by: a substrate-arrival detecting sensor for detecting the mounted substrate transferred into the substrate discharge-waiting process; and a substrate-continuity detecting sensor, provided in the upstream of the substrate-arrival detecting sensor, for detecting the unmounted substrate transferred continuously with the mounted substrate. Thus, the detecting means can be formed by less number of sensors at a lower cost because the substrate-detected state of the substrate-continuity sensor is obtained when the substrate-arrival sensor detected substrate. Therefore, the second aspect of the present invention has an effect that the transfer of the unmounted substrate to the downstream equipment, that may occur when a plurality of substrates were continuously transferred into the following process, and the occurrence of the defective substrate caused by that transfer can be prevented in advance.

A third aspect of the present invention is to arrange the substrate-continuity detecting sensor at a position that satisfies X<XS<2X, where a distance from the substrate-arrival detecting sensor to the substrate-continuity detecting sensor is XS and a substrate dimension in a substrate transfer direction is X. Thus, the detecting means can be formed by less number of sensors without adjustment of sensors for every change of product type because the substrate-detected state of the substrate-continuity detecting sensor is obtained when the substrate-arrival detecting sensor detected substrate. Therefore, the third aspect of the present invention has an effect that the transfer of the unmounted substrate to the downstream equipment, that may occur when a plurality of substrates were continuously transferred into the following process, and the occurrence of the defective substrate caused by that transfer can be prevented in advance.

A fourth aspect of the present invention is to arrange the substrate-continuity detecting sensor to be movable. Thus, the substrate-continuity detecting sensor can be moved by hand and fixed to a given position in accordance with the substrate dimension X in a substrate transfer direction.

A fifth aspect of the present invention is to arrange the substrate-continuity detecting sensor to automatically move to a position that satisfies X<XS<2X in accordance with the substrate dimension X in the substrate transfer direction. Thus, the substrate-continuity sensor can be arranged without adjustment of the sensor for every change of the product type.

Moreover, a sixth aspect of the present invention is to form the detecting means by: the substrate-arrival detecting sensor for detecting the mounted substrate transferred into the substrate discharge-waiting process; and a plurality of substrate-continuity detecting sensors, provided in the upstream of the substrate-arrival detecting sensor at different positions in the substrate transfer direction from each other, for detecting the unmounted substrate that has been transferred continuously with the mounted substrate. Thus, a recovery function can be provided in which only the unmounted substrate is brought back to the mounting process by transferring the unmounted substrate in the reverse direction and thereafter the mounted substrate is transferred to the position of the substrate-arrival detecting sensor in the substrate discharge-waiting process by the transfer in the normal direction.

In addition, a seventh aspect of the present invention is to arrange the substrate-continuity detecting sensors to detect the unmounted substrate by a substrate-detection state of one of the plurality of substrate-continuity detecting sensors that is located at the position satisfying X<XS<2X, where a distance from the substrate-arrival detecting sensor to the one substrate-continuity detecting sensor is XS and a substrate dimension in the substrate transfer direction is X. Therefore, the seventh aspect of the present invention has an effect that the transfer of the unmounted substrate to the downstream equipment, that may occur when a plurality of substrates were continuously transferred into the following process, and the occurrence of the defective substrate caused by that transfer can be prevented in advance by obtaining the substrate-detected state of one of the plurality of substrate-continuity detecting sensors which has such a distance XS from the substrate-arrival detecting sensor that X<XS<2X is satisfied.

Furthermore, as in an eighth aspect of the present invention, the substrate transfer apparatus is formed by the minimum required number of the substrate-continuity detecting sensors by arranging N sensors that satisfy 2^(N)×P_min>P_max at positions determined by 2^(n)×P_min 2(n=1, 2, . . . , N) from the minimum substrate size (P_min) and the maximum substrate sizes (P_max) in the substrate transfer direction, respectively, for which the electronic component mounting machine is intended. In this case, the substrate dimension from the minimum substrate size to the maximum substrate size can be obtained in an appropriate manner.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an electronic component mounting machine including a substrate transfer apparatus that has a substrate-continuity detecting sensor, according to one example of an embodiment of the present invention;

FIG. 2 is a view of a substrate discharge-waiting process in a first embodiment of the present invention, seen from above the substrate discharge-waiting process;

FIG. 3 is a view of the substrate discharge-waiting process in a second embodiment of the present invention, seen from above the substrate discharge-waiting process;

FIGS. 4A-4C are views showing the arrangement of the substrate-continuity detecting sensors in the substrate discharge-waiting process in the second embodiment of the present invention, seen from above the substrate discharge-waiting process;

FIG. 5 is a perspective view of an electronic component mounting machine including a conventional substrate transfer apparatus;

FIGS. 6A-6D are sequential diagrams showing a substrate transfer process in the conventional substrate transfer apparatus;

FIGS. 7A-7D are sequential diagrams showing a simultaneous substrate transfer process in the conventional substrate transfer apparatus; and

FIGS. 8A-8D are sequential diagrams showing a process in which a trouble occurs when substrates are simultaneously transferred in the conventional substrate transfer apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Hereinafter, first to fifth aspects of the present invention are described with reference to a first embodiment.

FIG. 1 is a perspective view of an electronic component mounting machine for mounting electronic components, as an exemplary component mounting machine according to an embodiment, and FIG. 2 is a view of a substrate discharge-waiting process 9 in the first embodiment, seen from above the substrate discharge-waiting process 9.

In FIG. 1, the reference numeral 1 denotes an electronic component mounting machine. In this electronic component mounting machine 1, a mounting-waiting process 7, a mounting process 8, and a substrate discharge-waiting process 9 are provided. The reference numeral 2 denotes a mounted substrate while 3 denotes an unmounted substrate. In the substrate discharge-waiting process 9, a substrate-arrival detecting sensor 5 c and a substrate-continuity detecting sensor 6 are arranged.

The unmounted substrate 3 that has been carried in the substrate discharge-waiting process 9, shown in FIG. 2, is a substrate which is to be stopped in the mounting process 8, that is the previous process, normally but has been carried into the substrate discharge-waiting process 9 continuously with the mounted substrate 2. In FIG. 2, the substrate dimension (X) in a substrate transfer direction is obtained from a substrate program in which dimension data of substrates has been set. The substrate-continuity detecting sensor 6 is movable by hand to any given position along the substrate transfer direction indicated by the arrow in FIG. 1, so as to be fixed at the given position along the substrate transfer direction. The substrate dimension (X) in the substrate transfer direction has been obtained during production, and, of course, the dimensions (X) of the mounted substrate 2 and unmounted substrate 3 in the substrate transfer direction are equal to each other. XS represents the distance from the detector portion of the substrate-arrival detecting sensor 5 c to the detector portion of the substrate-continuity detecting sensor 6. In a case where the substrate-continuity detecting sensor 6 is fixed at the position that satisfies X<XS<2X, when the substrate-continuity detecting sensor 6 is in a substrate-detected state after the substrate-arrival detecting sensor 5 c detected a substrate and caused the transfer belt to stop, transferring of a plurality of substrates into the substrate discharge-waiting process 9 is determined. By dealing with the errors after that determination, it is possible to prevent the unmounted substrate 3 from being discharged to the following process, i.e., another equipment connected to the downstream, in advance.

Although the value of the substrate dimension (X) in the substrate transfer direction is obtained from the substrate program in the first embodiment, this value is obtained by measurement using a substrate-passing detection timer, a device for detecting the rotation rate of transfer belt and a timer for measuring a substrate-passing time in an alternative embodiment.

Moreover, the substrate-continuity detecting sensor 6 is movable by hand in the first embodiment. However, it is possible to achieve the same effect in a case where the substrate-continuity detecting sensor 6 is arranged to be automatically movable to an adequate position in accordance with the substrate dimension (X) in the substrate transfer direction.

In addition, the substrate-continuity detecting sensor 6 is provided in the substrate discharge-waiting process 9 that is the final process of the substrate transfer process in the first embodiment. However, it is possible to obtain the same effect even in a case where the substrate-continuity detecting sensor 6 is provided in any of other processes if as long as the substrate transfer apparatus is arranged in such a manner that a plurality of substrates waits before a certain process and there is a possibility that a plurality of substrates are transferred into the certain process.

Furthermore, in the first embodiment, the errors are dealt after the substrate-continuity detecting sensor 6 detected that a plurality of substrates were transferred to the following process. However, it is possible to provide additional substrate-continuity detecting sensor 6 in the process before the process in which the substrate-arrival detecting sensor 5 c is provided, i.e., the mounting process 8 in the first embodiment. Referring to FIG. 6 showing the conventional example, it is also possible to provide a recovery function in which only the unmounted substrate 3 is brought back to the mounting process 8 by rotating the transfer belts 10 b and 10 c in the reverse direction and the mounted substrate 2 is transferred to the position of the substrate-arrival detecting sensor 5 c in the discharge-waiting process 9 by rotating the transfer belt 10 c in the discharge-waiting process 9 only in the normal direction.

Embodiment 2

Sixth to eighth aspects of the present invention are described with reference to a second embodiment. FIG. 3 is a view of the substrate discharge-waiting process 9 in the second embodiment, seen from above the process 9. FIGS. 4A-4C are views of the substrate discharge-waiting process 9 in the second embodiment, seen from above the process 9, showing the arrangement of substrate-continuity detecting sensors 6 a, 6 b, and 6 c in the second embodiment.

In FIG. 3, the difference from the first embodiment is that a plurality of substrate-continuity detecting sensors are provided and the substrate-detected state of the substrate-continuity detecting sensor, which is located at the position allowing detection of the continuity of the substrates, is referred to in accordance with the substrate dimension (X) in the substrate transfer direction.

In FIG. 3, in the substrate discharge-waiting process 9, a substrate-arrival detecting sensor 5 c and three substrate-continuity detecting sensors 6 a, 6 b, and 6 c are provided. The sensors are arranged at positions determined by 2^(n)×P_min (n=1, 2, . . . , N) from the minimum substrate size (P_min) and maximum substrate size (P_max) for which this electronic component mounting machine is intended. Moreover, the substrate dimension (X) in the substrate transfer direction is obtained from the substrate program in which the dimension data of substrate has been set. This value X was obtained during production, and the substrate dimensions (X) in the substrate transfer direction of the mounted substrate 2 and the unmounted substrate 3 are equal to each other. XS is a distance from the detector portion of the substrate-arrival detecting sensor 5 c to the detector portion of one of the substrate-continuity detecting sensors 6 a-6 c that is used for detection in accordance with the substrate dimension (X) in the substrate transfer direction.

When the substrate-arrival detecting sensor 5 c detected the mounted substrate 2 and caused the transfer belt 10 c (see FIG. 6B) to be halted and thereafter one of the substrate-continuity detecting sensors 6 a-6 c, which is located at the position satisfying X<XS<2X, is in the substrate-detected state, it is possible to determine a plurality of substrates being carried into the substrate discharge-waiting process 9. By dealing with the errors thereafter, it is possible to prevent the unmounted substrate 3 from being discharged to another equipment connected to the downstream of the process 9.

FIGS. 4A-4C show details of the arrangement of the substrate-continuity detecting sensors 6 a-6 c in the second embodiment. FIG. 4A shows that the substrate-continuity detecting sensor 6 a is capable of detecting the continuity of substrates each having the dimension (X) in the substrate transfer direction in a range from the minimum substrate size (P_min) to (2×P_min). FIG. 4B shows that the substrate-continuity detecting sensor 6 b is capable of detecting the continuity of substrates each having the dimension (X) in the substrate transfer direction in a range from (2×P_min) to (4×P_min). FIG. 4C shows that the substrate-continuity detecting sensor 6 c is capable of detecting the continuity of substrates each having the dimension (X) in the substrate transfer direction in a range from (4×P_min) to (P_max). By arranging the substrate-continuity sensors in the above-mentioned manner, the substrate dimension from the minimum substrate size to the maximum substrate size for which the electronic component mounting machine 1 is intended, is covered by N sensors, N being the minimum required number obtained from 2^(N)×P_min>P_max.

It is assumed that the minimum and maximum substrate dimensions in the substrate transfer direction for which the electronic component mounting machine 1 is intended are 50 mm and 330 mm, respectively. In this case, the necessary number of the substrate-continuity detecting sensors is at least three. By arranging the substrate-continuity detecting sensors at positions separated from the substrate-arrival detecting sensor 5 c by 100 mm, 200 mm, and 400 mm, respectively, a detection device formed by these sensors for detecting that a plurality of substrates have been continuously carried in detects the continuity of substrates for all the substrate dimensions for which the electronic component mounting machine 1 is intended.

In the second embodiment, the substrate-continuity detecting sensors 6 are arranged at the positions determined by 2^(n)×P_min (n=1, 2, . . . , N). However, in order to more stably detect that a plurality of substrates have been carried in, the arrangement of the sensors may be provided with margin. When this margin is assumed to be (á), it is possible to construct a detecting means with more stability for detecting a plurality of substrates continuously carried in by arranging N sensors at the positions determined by 2^(n)×P_min−á, N being obtained from 2^(N)×P_min>P_max−á.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, in a case where a plurality of substrates are transferred simultaneously, it can be determined by detecting means whether or not a plurality of substrates have been continuously carried in from the previous process. Thus, the problems caused when a plurality of substrates have been discharged to the following process, that an unmounted substrate may be discharged to another equipment connected to the downstream and therefore a defective substrate is generated, can be prevented in advance. Therefore, the present invention is suitable for improving the quality of manufactured substrates while the substrate transfer time is reduced. 

1. A substrate transfer apparatus for a component mounting machine, for transferring a substrate into a mounting process in which components are mounted onto the substrate and transferring the substrate from said mounting process, comprising: a mounting-waiting process for making the substrate to be transferred into the mounting process wait before the mounting process; and a substrate discharge-waiting process for making the substrate after being transferred from the mounting process wait before a following process, wherein transfer of an unmounted substrate from said mounting-waiting process to the mounting process and transfer of a mounted substrate for which mounting has been done in the mounting process from the mounting process to the substrate discharge-waiting process are performed simultaneously, characterized in that detecting means are provided for detecting that a plurality of substrates have been transferred into the substrate discharge-waiting process as part of the same transfer.
 2. The substrate transfer apparatus for a component mounting machine according to claim 1, wherein the detecting means includes: a substrate-arrival detecting sensor for detecting the mounted substrate transferred into the substrate discharge-waiting process; and a substrate-continuity detecting sensor, provided upstream of the substrate-arrival detecting sensor, for detecting an unmounted substrate being transferred at the same time as the mounted substrate.
 3. The substrate transfer apparatus for a component mounting machine according to claim 2, wherein the substrate-continuity detecting sensor is arranged at a position that satisfies X<XS<2X, where a distance from the substrate-arrival detecting sensor to the substrate-continuity detecting sensor is XS and a substrate dimension in the substrate transfer direction is X.
 4. The substrate transfer apparatus for a component mounting machine according to claim 3, wherein the substrate-continuity detecting sensor is arranged to be movable to the position that satisfies X<XS<2X.
 5. The substrate transfer apparatus for a component mounting machine according to claim 3, wherein the substrate-continuity detecting sensor is constructed to be automatically movable to the position that satisfies X<XS<2X, in accordance with the substrate dimension X in the substrate transfer direction.
 6. The substrate transfer apparatus for a component mounting machine according to claim 1, wherein the detecting means includes: a substrate-arrival detecting sensor for detecting the mounted substrate transferred into the substrate discharge-waiting process; and a plurality of substrate-continuity detecting sensors, provided upstream of the substrate-arrival detecting sensor at different positions in a substrate transfer direction from one another, for detecting an unmounted substrate being transferred at the same time as the mounted substrate.
 7. The substrate transfer apparatus for a component mounting machine according to claim 6, wherein the substrate-continuity detecting sensors detect an unmounted substrate by a substrate-detection state of one of the plurality of substrate-continuity detecting sensors that is located at a position satisfying X<XS<2X, where a distance from the substrate-arrival detecting sensor to the one substrate-continuity detecting sensor is XS and a substrate dimension in the substrate transfer direction is X.
 8. The substrate transfer apparatus for a component mounting machine according to claim 6, wherein the substrate transfer apparatus includes a minimum required number of the substrate-continuity detecting sensors by arranging N sensors that satisfy 2^(N)×P_min>P_max at positions determined by 2^(n)×P_min 2(n=1, 2, . . . , N) from a minimum substrate size (P_min) and a maximum substrate size (P_max) in the substrate transfer direction, respectively, for which the electronic component mounting machine is intended.
 9. The substrate transfer apparatus for a component mounting machine according to claim 7, wherein the substrate transfer apparatus includes a minimum required number of the substrate-continuity detecting sensors by arranging N sensors that satisfy 2^(N)×P_min>P_max at positions determined by 2^(n)×P_min 2(n=1, 2, . . . , N) from a minimum substrate size (P_min) and a maximum substrate size (P_max) in the substrate transfer direction, respectively, for which the electronic component mounting machine is intended. 